Slide masters are pretty great – they allow you to streamline your production by housing objects and/or triggers you want to be fired on top of all slides there. However, when it comes to accessibility and focus or tab orders, slide masters can have some nuances. Any object you place on a slide master will by default appear in the focus order and you cannot delete them from the focus order using the Custom order functionality. To remove these objects from appearing on all slide focus orders, you must do this at the slide master level.
Check out the screencast below!